Non-oriented electrical steel sheet and manufacturing method thereof

ABSTRACT

An inorganic-organic composite film is formed by coating a application liquid containing an inorganic component and an organic resin on a surface of a steel sheet, and baking the application liquid on the surface of the steel sheet. The application liquid contains phosphate as the inorganic component, and further contains an inorganic powder having a BET specific surface area of 10 m 2 /g or more and exhibiting a particle size distribution with a 50% cumulative particle size of 5 μm or less and with a 90% cumulative particle size of 15 μm or less when measured by a laser diffraction particle size analyzer, the powder being contained at a ratio of no less than 1 mass %, nor more than 50 mass % with respect to a solid content of the phosphate.

TECHNICAL FIELD

The present invention relates to a non-oriented electrical steel sheethaving a small environmental load and a manufacturing method thereof.

BACKGROUND ART

A non-oriented electrical steel sheet is used as an iron core materialfor motor, for example. In this case, a plurality of non-orientedelectrical steel sheets are stacked on one another, so that they have tobe insulated one from another. For this reason, insulating films areformed on surfaces of the non-oriented electrical steel sheets. As amaterial of the insulating film, a compound containing chromate has beenused.

However, chromium is likely to cause environmental pollution. Therefore,in recent years, there has been conducted a research regarding a formingmethod of a film using a compound which does not contain chromate. Sucha film is sometimes referred to as an environment-responsive coating.

A technique regarding the environment-respective coating can beclassified broadly into two types, based on a difference of inorganiccomponent to be used. One is a technique in which colloidal silica isused as a main inorganic component, and the other is a technique inwhich phosphate is used as a main inorganic component.

However, in conventional non-oriented electrical steel sheets havingfilms containing phosphate, if the non-oriented electrical steel sheetsare stacked on one another over a long period at room temperature ortemperature a little higher than the room temperature, the films maybecome sticky, or the films may adhere to one another.

For example, the non-oriented electrical steel sheets having the filmsformed thereon are sometimes transported by ships. In this case, thenon-oriented electrical steel sheets are disposed, in a hold, in a stateof “being rolled in a coil shape” and axial centers of coils becomehorizontal, namely, in a state where “the rolled sheets are aligned sideby side”. At this time, a large surface pressure applies to the mutuallycontacted films, and this state is maintained over a long period.

Further, when an adhesion occurs under this state, it becomes difficultto release the rolled state of the non-oriented electrical steel sheetsat a customer.

Although there are various techniques regarding theenvironmental-responsive coating (Patent Documents 1 to 29), it is notpossible to effectively suppress the adhesion in any of them.

Citation List Patent Literature

Patent Document 1: Japanese Laid-open Patent Publication No. 59-21927

Patent Document 2: Japanese Laid-open Patent Publication No. H9-122582

Patent Document 3: Japanese Laid-open Patent Publication No. H9-136061

Patent Document 4: Japanese Laid-open Patent Publication No. H9-314733

Patent Document 5: Japanese Laid-open Patent Publication No. H9-323066

Patent Document 6: Japanese Laid-open Patent Publication No. H9-327886

Patent Document 7: Japanese Laid-open Patent Publication No. H10-36976

Patent Document 8: Japanese Laid-open Patent Publication No. H10-34812

Patent Document 9: Japanese Laid-open Patent Publication No. H10-128903

Patent Document 10: Japanese Laid-open Patent Publication No. H10-128904

Patent Document 11: Japanese Laid-open Patent Publication No. H10-130858

Patent Document 12: Japanese Laid-open Patent Publication No. H10-130859

Patent Document 13: Japanese Laid-open Patent Publication No.2001-240916

Patent Document 14: Japanese Laid-open Patent Publication No.2004-197202

Patent Document 15: Japanese Laid-open Patent Publication No. H6-330338

Patent Document 16: Japanese Laid-open Patent Publication No. H7-41913

Patent Document 17: Japanese Laid-open Patent Publication No. H7-166365

Patent Document 18: Japanese Laid-open Patent Publication No. H11-80971

Patent Document 19: Japanese Laid-open Patent Publication No. H11-131250

Patent Document 20: Japanese Laid-open Patent Publication No. H11-152579

Patent Document 21: Japanese Laid-open Patent Publication No.2000-129455

Patent Document 22: Japanese Laid-open Patent Publication No. H10-15484

Patent Document 23: Japanese Laid-open Patent Publication No. H10-15485

Patent Document 24: Japanese Laid-open Patent Publication No. H10-46350

Patent Document 25: Japanese Laid-open Patent Publication No. H10-130857

Patent Document 26: Japanese Laid-open Patent Publication No. H9-316655

Patent Document 27: Japanese Laid-open Patent Publication No.2004-322079

Patent Document 28: Japanese Laid-open Patent Publication No. 2000-26979

Patent Document 29: Japanese Laid-open Patent Publication No.2004-107796

SUMMARY OF THE INVENTION Technical Problem

An object of the present invention is to provide a non-orientedelectrical steel sheet capable of effectively suppressing adhesion evenif a film thereof contains phosphate, and a manufacturing methodthereof.

Solution to Problem

The present inventors analyzed an adhesion as will be described laterand started to set out a solution. As a result of this, the presentinventors found out that the occurrence of adhesion is effectivelysuppressed by making a application liquid for forming film contain aspecified inorganic powder so that the ceramics powder absorbs orimmobilizes free phosphoric acid generated in accordance with adehydration/condensation reaction. Further, the present inventors alsofound out that it is preferable to previously reduce phosphate groups inthe application liquid within a range in which a desired property can beobtained, in order to reduce the amount of free phosphoric acid.

The present invention has been made based on these findings, and thegist thereof is as follows.

(1) A manufacturing method of a non-oriented electrical steel sheet,including:

coating an application liquid which contains an inorganic component andan organic resin on a surface of a steel sheet; and

forming an inorganic-organic composite film by baking the applicationliquid on the surface of the steel sheet,

wherein the application liquid contains phosphate as the inorganiccomponent, and

wherein the application liquid further contains an inorganic powderhaving a BET specific surface area of 10 m²/g or more and exhibiting aparticle size distribution with a 50% cumulative particle size of 5 μmor less and with a 90% cumulative particle size of 15 μm or less whenmeasured by a laser diffraction particle size analyzer, the powder beingcontained at a ratio of no less than 1 mass %, nor more than 50 mass %with respect to a solid content of the phosphate.

(2) The manufacturing method of a non-oriented electrical steel sheetaccording to (1), wherein the application liquid does not contain achromate-based compound.

(3) The manufacturing method of a non-oriented electrical steel sheetaccording to (1) or (2), wherein the application liquid contains, as theinorganic powder, at least one kind selected from a group consisting ofalumina powder, silica powder, magnesia powder, titanic powder andzirconia powder.

(4) The manufacturing method of a non-oriented electrical steel sheetaccording to any one of (1) to (3), wherein the application liquid isformed of a mixed solution of an aqueous aluminum biphosphate solutionand an aqueous dispersion of organic resin, and the inorganic powder.

(5) The manufacturing method of a non-oriented electrical steel sheetaccording to any one of (1) to (4), wherein a temperature at the bakingthe application liquid on the surface of the steel sheet is set to 270°C. or higher.

(6) A non-oriented electrical steel sheet, including aninorganic-organic composite film formed on a surface,

wherein the inorganic-organic composite film contains:

phosphate; and

an inorganic powder having a BET specific surface area of 10 m²/g ormore and exhibiting a particle size distribution with a 50% cumulativeparticle size of 5 μm or less and with a 90% cumulative particle size of15 μm or less when measured by a laser diffraction particle sizeanalyzer, and

wherein a content of the inorganic powder is no less than 1 mass %, normore than 50 mass % with respect to a solid content of the phosphate.

(7) The non-oriented electrical steel sheet according to (6), whereinthe inorganic-organic composite film does not contain a chromate-basedcompound.

(8) The non-oriented electrical steel sheet according to (6) or (7),wherein the inorganic-organic composite film contains, as the inorganicpowder, at least one kind selected from a group consisting of aluminapowder, silica powder, magnesia powder, titania powder and zirconiapowder.

(9) An application liquid for a non-oriented electrical steel sheet,containing:

phosphate as an inorganic component; and

an inorganic powder having a BET specific surface area of 10 m²/g ormore and exhibiting a particle size distribution with a 50% cumulativeparticle size of 5 μm or less and with a 90% cumulative particle size of15 μm or less when measured by a laser diffraction particle sizeanalyzer, the powder being contained at a ratio of no less than 1 mass%, nor more than 50 mass % with respect to a solid content of thephosphate.

(10) The application liquid for a non-oriented electrical steel sheetaccording to (9), wherein a chromate-based compound is not contained.

(11) The application liquid for a non-oriented electrical steel sheetaccording to (9) or (10), wherein at least one kind selected from agroup consisting of alumina powder, silica powder, magnesia powder,titania powder and zirconia powder is contained as the inorganic powder.

Advantageous Effects of Invention

According to the present invention, since a application liquid containsa specified inorganic powder, even if a film contains phosphate, it ispossible to effectively suppress adhesion.

DESCRIPTION OF EMBODIMENTS

First, details of how the present inventors completed the presentinvention will be described.

The present inventors focused attention on a chemical change at the timewhen phosphate is baked on a surface of a steel sheet (steel basematerial), and analyzed the chemical reaction. Note that the chemicalreaction of phosphate is so complicated that it has not been clarifiedyet on a scientific study.

When an aqueous phosphate solution containing Al is heated, adehydration/condensation reaction occurs. In thedehydration/condensation reaction, phosphorus components and Alcomponents are solidified while mutually forming networks. As a resultof that, an inorganic film coating on the surface of the steel sheet isformed. Here, the dehydration/condensation reaction will be described byciting aluminum biphosphate as an example.

When aluminum biphosphate is heated, a reaction as in the equation (1)proceeds.

Al(H₂PO₄)₃→AlPO₄+H_(x)PO_(y)   equation (1)

From the equation (1), it can be seen that when forming a film using thedehydration/condensation reaction of aluminum biphosphate, a phosphoricacid component which is not bonded to a metal component, that is,aluminum, namely, free phosphoric acid is by-produced in accordance withthe proceeding of the dehydration/condensation reaction.

The present inventors thought that an adhesion phenomenon occurred instacked non-oriented electrical steel sheets is caused by the freephosphoric acid, and earnestly investigated a reaction mechanism of theadhesion phenomenon.

When non-oriented electrical steel sheets are stacked, a certain amountof gap exists between the respective steel sheets. Therefore, it isquite possible that moisture enters the gap from an ambient atmosphere.

Meanwhile, when free phosphoric acid exists in a film, since the freephosphoric acid is not bonded to a metal component, it is chemicallyunstable and is highly likely to react with another component.Therefore, it is quite possible that the free phosphoric acid in thefilm reacts with the moisture that entered the gap. Further, when thefree phosphoric acid reacts with the moisture, a kind of swellingreaction occurs in the film, which results in causing stickiness.

When the stickiness is caused in a state where a pressure acts onsurfaces of non-oriented electrical steel sheets such as a state wherethe non-oriented electrical steel sheets are rolled in a coil shape,films are adhered to each other, which results in creating a state wherethe non-oriented electrical steel sheets are adhered to each other.

The present inventors thought that if it is possible to inhibit stickingreaction with the moisture by inactivating or immobilizing the freephosphoric acid, an adhesion phenomenon occurred in an inorganic-organiccomposite film containing no chromate-based compound can be suppressed.

Through further and repeated earnest investigation, the presentinventors thought to previously make an application liquid used forforming the inorganic-organic composite film without chromate-basedcompound contain an inorganic powder such as ceramics so that freephosphoric acid generated in a dehydration/condensation reaction isabsorbed and immobilized by the inorganic powder. Specifically, thepresent inventors thought that even if free phosphoric acid is generatedfrom phosphate through the dehydration/condensation reaction, theoccurrence of stickiness and adhesion phenomenon may be prevented bymaking the free phosphoric acid to be absorbed on a surface of theinorganic powder to immobilize the free phosphoric acid.

Note that not only free phosphoric acid generated from phosphate aftermanufacturing non-oriented electrical steel sheets on which films areformed, but also free phosphoric acid in an application liquid used forforming the films may cause the stickiness and adhesion phenomenon.Conventionally, a phosphoric acid-rich solution formed by further addingphosphoric acid to an aqueous phosphate solution has been sometimes usedto prevent precipitation of a phosphate crystal during the storage ofthe aqueous phosphate solution, but, in the present invention, it ispreferable not to use such phosphoric acid-rich aqueous phosphatesolution.

Further, the present inventors conducted various experiments asdescribed as follows based on these views.

(BET Specific Surface Area)

The present inventors thought that efficiency for capturing freephosphoric acid generated in a film using an inorganic powder is largelyaffected by a surface area of the inorganic powder. Therefore, aluminapowders with various surface areas were prepared and used for theexperiments.

Among inorganic powders, an alumina powder is relatively inexpensive.Further, products with variety of surface areas ranging from small tolarge are on the market, and it is easy to obtain alumina powders withvarious surface areas. Accordingly, the present inventors selected thealumina powder among various inorganic powders as a first evaluationtarget.

The surface area of the alumina powder was evaluated using a BET(Brunauer, Emmett, Teller) method. A measurement method of a specificsurface area using the BET method is commonly used as an evaluationmethod of a surface area of an inorganic powder. The BET method is amethod of measuring, by making a powder absorb, for example, nitrogengas of which absorption occupied area is known on a surface thereof, asurface area of the powder based on an absorption amount and a pressurechange. Since the surface area is normally represented by a surface area(m²) per unit weight (g) of a powder, it is called a specific surfacearea that has a unit of “m²/g”.

Further, the present inventors conducted experiments described asfollows, in order to understand a suppress effect of the BET specificsurface area of the alumina powder on the adhesion phenomenon.

First, steel sheets were cold-rolled to a thickness of 0.5 mm and thenannealed at 900° C., thereby producing a plurality of steel sheets onwhich films were not formed.

Further, there were prepared application liquids each formed by adding 5g of alumina powder to a mixed solution of 100 g of an aqueous aluminumbiphosphate solution having a concentration of 50 mass % and 40 g of anaqueous dispersion of acrylic organic resin having a concentration of 30mass %. At this time, nine types of alumina powders each having adifferent BET specific surface area were used. Further, as the aluminapowders, ones having a 50% cumulative particle size of 0.15 μm and a 90%cumulative particle size of 0.73 μm regarding a particle sizedistribution measured by using a laser diffraction particle sizeanalyzer were used, regardless of the BET specific surface area.

Further, the application liquids were coated on surfaces of the steelsheets and dried under a condition where an achieving temperature of thesteel sheets became 300° C. A coating amount of the application liquidwas set so that an amount of film after the drying (after the baking)became 2.5 g/m² per one side of the steel sheet.

A measurement method of particle size distribution using a laserdiffraction particle size analyzer is commonly used as an evaluationmethod of particle size distribution of an inorganic powder. In thismeasurement method, a powder to be a measurement target is dispersed ina solvent such as water, and the solvent in which the powder isdispersed is placed in the laser diffraction particle size analyzer. Thelaser beam with specific wavelength was irradiated to the dispersion,analyzed scattered light and diffracted light from the dispersion,converted the analysis result into a particle size distribution andoutput it. Hereinafter, the term particle size distribution indicates aparticle size distribution (including 50% cumulative particle size and90% cumulative particle size) measured by the laser diffraction particlesize analyzer, unless otherwise stated.

Adhesion of thus produced non-oriented electrical steel sheets withfilms was evaluated in a procedure described as follows.

First, a large number of samples each having a size of 30 mm×40 mm werecut out from a non-oriented electrical steel sheet. Subsequently, thesesamples were stacked so that a long side and a short side werealternately disposed, pressurized at a surface pressure of 40 kg/cm²,and fixed under a pressurized state. Specifically, surfaces of thenon-oriented electrical steel sheets were contacted to one another in anarea of 30 mm×30 mm, namely, in an area of 9 cm². The number of stackednon-oriented electrical steel sheets was set to ten under one condition.

Thereafter, ten pieces of non-oriented electrical steel sheets were put,while being fixed, into a thermo-hygrostat in which the temperature waskept at 50° C. and the humidity was kept at 90%. This state simulated asituation where the non-oriented electrical steel sheets rolled in acoil shape are being transported.

The non-oriented electrical steel sheets were taken out, at a time pointat which one week has passed after the steel sheets were put into thethermo-hygrostat, and were cooled to room temperature. Thereafter, thepressurized state was released, and the non-oriented electrical steelsheets were peeled off one by one. Namely, the nine times of peelingwere conducted for each stack of the ten pieces of non-orientedelectrical steel sheets. At this time, a force required for the peelingwas measured by using a spring scale, and an average value (peel force)of the nine times of peeling was calculated. Results thereof are shownin Table 1. Smaller peel force value indicates that the stickiness andadhesion phenomenon were unlikely to occur, and larger peel force valueindicates that the stickiness and adhesion phenomenon were likely tooccur. Accordingly, in Table 1, an evaluation in which the peel forcewas less than 50 g was represented by ⊚, an evaluation in which the peelforce was not less than 50 g and less than 100 g was represented by ◯,and an evaluation in which the peel force was 100 g or more wasrepresented by ×.

TABLE 1 BET SPECIFIC SURFACE AREA OF ALUMINA POWDER PEEL FORCE NUMBER(m²/g) (g) DETERMINATION A (1) 0.5 825 X A (2) 3.7 445 X A (3) 10.0 72 ◯A (4) 28.1 63 ◯ A (5) 40.0 41 ⊚ A (6) 101.6 35 ⊚ A (7) 250.3 25 ⊚ A (8)340.4 27 ⊚ A (9) 450.0 21 ⊚

As shown in Table 1, under conditions of numbers A(1) and A(2) eachusing the alumina powder whose BET specific surface area was less than10 m²/g, the peel forces were very large to be 825 g and 445 g,respectively. This indicates that the films were adhered to one anotherin the thermo-hygrostat.

Meanwhile, under conditions of numbers A(3) to A(9) each using thealumina powder whose BET specific surface area was 10 m²/g or more, thepeel forces were small to be 72 g to 21 g. This indicates that thestickiness and adhesion phenomenon were effectively prevented. Inparticular, under the conditions of the numbers A(5) to A(9) each usingthe alumina powder whose BET specific surface area was 40 m²/g or more,the peel forces were quite small to be less than 50 g. This indicatesthat the effect of preventing the stickiness and adhesion phenomenonunder these conditions is particularly excellent.

From the above results, it was confirmed that the BET specific surfacearea of the alumina powder is only required to be 10.0 m²/g or more inorder to suppress the stickiness and adhesion phenomenon. Further, itwas also confirmed that the effect of suppressing the stickiness andadhesion phenomenon is particularly excellent when the BET specificsurface area of the alumina powder is 40 m²/g or more.

(Particle Size Distribution)

Next, the present inventors examined the affect of particle sizedistribution of an inorganic powder to be added, by conductingexperiments described below.

Here, description on how the particle size distribution affects theproperty of the non-oriented electrical steel sheet will be made.

The non-oriented electrical steel sheet according to the presentinvention is used, for example, as an iron core material for electricequipment, particularly, as an iron core material for rotating machine(motor). In this case, a plurality of non-oriented electrical steelsheets are sometimes stacked on one another.

One of reasons why the non-oriented electrical steel sheet is used asthe iron core material for rotating machine is a high magnetic fluxdensity thereof. The iron core material for rotating machine is requiredto efficiently introduce a magnetic flux within the iron core whenelectric energy is converted into mechanical energy in accordance withthe law of electrical induction. Specifically, the iron core materialfor rotating machine is required to have a high magnetic flux density.The non-oriented electrical steel sheet satisfies the requirement.

Therefore, a stack formed by stacking a plurality of non-orientedelectrical steel sheets is also required to have a high magnetic fluxdensity. A gap exists, to no small extent, between the non-orientedelectrical steel sheets, and the magnetic flux density is lowered as thegap is larger. This is because the magnetic flux density in the airexisting in the gap is significantly low. Therefore, in a film of anon-oriented electrical steel sheet, it is required that a convexportion is small and the number thereof is small in order not togenerate the gap as described above.

Specifically, it is unfavorable for the non-oriented electrical steelsheets, which are stacked to be used to have coarse convex portions onsurfaces of films thereof.

However, when the inorganic powders such as alumina powders are added tothe application liquid as described above, it is conceivable that a partof the inorganic powders is positioned on the surface of the film.Further, for example, even when a large part of the inorganic powderscontained in the application liquid are small, if coarse powders arecontained, convex portions ascribable to such coarse powders may bescattered on the surface of the film. In this case, a size of the gapbetween the non-oriented electrical steel sheets is varied by the convexportions.

For this reason, it is important to set a particle size distributionincluding a particle size, in particular, even a portion of a largeparticle size of the inorganic powder, to fall within an appropriaterange.

Accordingly, the present inventors defined the particle sizedistribution based on a 50% cumulative particle size and a 90%cumulative particle size measured by a laser diffraction particle sizeanalyzer.

Here, the 50% cumulative particle size corresponds to a particle size,in a particle size distribution formed from a population of inorganicpowder, when a mass is integrated in the order of smaller particle sizesand the integrated value reaches 50% of a total mass of the population.Further, the 90% cumulative particle size corresponds to a particle sizewhen the integrated value of the mass reaches 90% of the total mass ofthe population.

Accordingly, it is conceivable that the 50% cumulative particle sizeindicates a value close to an average particle size of the population,and the 90% cumulative particle size indicates a value close to anapproximate particle size of a coarse particle fraction in thepopulation.

Further, the present inventors conducted experiments regarding arelation between the particle size distribution of alumina powder and asurface roughness Ra (centerline average roughness) of a film.

First, steel sheets were cold-rolled to a thickness of 0.15 mm and thenannealed at 1050° C., thereby producing a plurality of steel sheets onwhich films were not formed.

Further, there were prepared application liquids each formed by adding 3g of alumina powder having a BET specific surface area of 120 m²/g to amixed solution of 100 g of an aqueous aluminum biphosphate solutionhaving a concentration of 50 mass % and 40 g of an aqueous dispersion ofacrylic organic resin having a concentration of 30 mass %. At this time,nine types of alumina powders each having different 50% cumulativeparticle size and 90% cumulative particle size were used.

Further, the application liquids were coated on surfaces of the steelsheets and dried under a condition where an achieving temperature of thesteel sheets became 320° C. A coating amount of the application liquidwas set so that an amount of film after the drying (after the baking)became 3.5 g/m² per one side of the steel sheet.

Thereafter, the surface roughness Ra of each of the non-orientedelectrical steel sheets was measured, and further, the peel force wasmeasured in the same manner as that of the above-described experiments.Results thereof are shown in Table 2. Also in Table 2, an evaluation inwhich the peel force was less than 50 g was represented by ⊚, anevaluation in which the peel force was not less than 50 g and less than100 g was represented by ◯, and an evaluation in which the peel forcewas 100 g or more was represented by ×. Further, regarding the surfaceroughness Ra, ⊚ represented an average roughness of 0.35 μm or less, ◯represented the average roughness which was more than 0.35 μm and was0.8 μm or less, and × represented the average roughness which was morethan 0.8 μm.

TABLE 2 PARTICLE SIZE DISTRIBUTION OF ALUMINA POWDER (μm) 50% 90%CUMULATIVE CUMULATIVE SURFACE PARTICLE PARTICLE PEEL FORCE ROUGHNESS RaCOMPREHENSIVE NUMBER SIZE SIZE (g) DETERMINATION (μm) DETERMINATIONDETERMINATION B (1) 0.25 0.62 42 ⊚ 0.21 ⊚ ◯ B (2) 0.32 1.13 37 ⊚ 0.23 ⊚◯ B (3) 0.49 1.55 45 ⊚ 0.29 ⊚ ◯ B (4) 1.64 5.0 28 ⊚ 0.35 ⊚ ◯ B (5) 2.258.6 35 ⊚ 0.39 ◯ ◯ B (6) 3.82 10.5 25 ⊚ 0.43 ◯ ◯ B (7) 5.00 15.0 28 ⊚0.63 ◯ ◯ B (8) 9.47 25.2 34 ⊚ 0.87 X X B (9) 13.8 43.5 21 ⊚ 1.52 X X

As shown in Table 2, the peel force was small to be less than 50 g underany of conditions of numbers B(1) to B(9). This is because the aluminapowder having the BET specific surface area of 120 m²/g was used.

Further, under the conditions of the number B(1) to the number B(7), inwhich the 50% cumulative particle size was 5 μm or less and the 90%cumulative particle size was 15 μm or less, the surface roughnesses Rawere small to be 0.21 μm to 0.63 μm. Specifically, no coarse convexportions were formed on the surfaces of the films, and thus a favorablestate was provided.

On the other hand, under the conditions of the number B(8) and thenumber B(9), in which the 50% cumulative particle size was more than 5.0μm and the 90% cumulative particle size was more than 15.0 μm, thesurface roughnesses Ra were large to be 0.87 μm and 1.52 μm,respectively. Specifically, coarse convex portions were formed on thesurfaces of the films.

Accordingly, regarding the particle size distribution of the inorganicpowder such as alumina powder used in the present invention, the 50%cumulative particle size is set to 5.0 μm or less, and the 90%cumulative particle size is set to 15.0 μm or less. Further, the 90%cumulative particle size is preferably 5.0 μm or less, and morepreferably 2.0 μm or less.

Note that from the perspective that the free phosphoric acid is absorbedto be immobilized by the inorganic powder such as alumina powder, thereis no lower limit to the 90% cumulative particle size of the inorganicpowder. However, since a significantly fine inorganic powder such asalumina powder is expensive, when cost is considered very important, the90% cumulative particle size is preferably set to 0.5 μm or more.

(Amount of Addition of Inorganic Powder)

The present inventors examined an effect of the amount of addition ofpowder.

First, steel sheets were cold-rolled to a thickness of 0.5 mm and thenannealed at 900° C., thereby producing a plurality of steel sheets onwhich films were not formed.

Further, there were prepared application liquids each formed by addingan alumina powder to a mixed solution of 100 g of an aqueous aluminumbiphosphate solution having a concentration of 50 mass % and 40 g of anaqueous dispersion of acrylic organic resin having a concentration of 30mass %. At this time, the amount of addition of the alumina powder wasvaried in nine ways. Further, as the alumina powder, one having a 50%cumulative particle size of 0.43 μm, a 90% cumulative particle size of2.32 μm, and a BET specific surface area of 100 m²/g was used.

Further, the application liquids were coated on surfaces of the steelsheets and dried under a condition where an achieving temperature of thesteel sheets became 310° C. A coating amount of the application liquidwas set so that an amount of film after the drying (after the baking)became 3.0 g/m² per one side of the steel sheet.

Thereafter, an appearance of each of the non-oriented electrical steelsheets was evaluated, and further, a peel force was measured in the samemanner as that of the above-described experiments. Results thereof areshown in Table 3. Also in Table 3, an evaluation in which the peel forcewas less than 50 g was represented by ⊚, an evaluation in which the peelforce was not less than 50 g and less than 100 g was represented by ◯,and an evaluation in which the peel force was 100 g or more wasrepresented by ×. Further, regarding the appearance, one that lookeduniform was represented by ◯, and one that looked non-uniformly whitewas represented by ×. Note that “ratio with respect to aluminumphosphate” in Table 3 indicates a ratio of a mass (g) of alumina powderwith respect to a solid content (g) of aluminum biphosphate contained inan aqueous aluminum biphosphate solution having a concentration of 50mass %. The concentration of the aqueous aluminum biphosphate solutionis 50 mass % and the mass thereof is 100 g, so that the solid content ofaluminum biphosphate is 50 g.

TABLE 3 ALUMINA POWDER RATIO WITH AMOUNT RESPECT TO OF AD- ALUMINUMDITION PHOSPHATE PEEL FORCE APPEARANCE OF FILM COMPREHENSIVE NUMBER (g)(MASS %) (g) DETERMINATION APPEARANCE DETERMINATION DETERMINATIONREMARKS C (1) 0.10 0.2 982 X UNIFORM AND ◯ X COMPARATIVE FAVORABLEEXAMPLE C (2) 0.25 0.5 504 X UNIFORM AND ◯ X COMPARATIVE FAVORABLEEXAMPLE C (3) 0.5 1.0 92 ◯ UNIFORM AND ◯ ◯ EXAMPLE FAVORABLE C (4) 1.02.0 83 ◯ UNIFORM AND ◯ ◯ EXAMPLE FAVORABLE C (5) 2.5 5.0 43 ⊚ UNIFORMAND ◯ ◯ EXAMPLE FAVORABLE C (6) 5.0 10.0 31 ⊚ UNIFORM AND ◯ ◯ EXAMPLEFAVORABLE C (7) 10.0 20.0 20 ⊚ UNIFORM AND ◯ ◯ EXAMPLE FAVORABLE C (8)25.0 50.0 14 ⊚ UNIFORM AND ◯ ◯ EXAMPLE FAVORABLE C (9) 37.5 75.0 12 ⊚NON- X X COMPARATIVE UNIFORMLY EXAMPLE WHITE

As shown in Table 3, under conditions of numbers C(1) and C(2), in whichthe ratio of Al with respect to phosphate was less than 1.0 mass %, thepeel forces were very large to be 982 g and 504 g, respectively. Thisindicates that the films were adhered to one another in thethermo-hygrostat.

On the other hand, under conditions of numbers C(3) to C(9), in whichthe ratio with respect to aluminum phosphate was 1.0 mass % or more, thepeel forces were small to be 92 g to 12 g. This indicates that thestickiness and adhesion phenomenon were effectively prevented. Inparticular, under the conditions of the numbers C(5) to C(9), in whichthe ratio with respect to aluminum phosphate was 5.0 mass % or more, thepeel forces were quite small to be 50 g or less. This indicates that theeffect of preventing the stickiness and adhesion phenomenon under theseconditions is particularly excellent.

Further, under the conditions of the numbers C(1) to C(8), in which theratio with respect to aluminum phosphate was 50.0 mass % or less, auniform and favorable appearance was observed.

On the other hand, in the number C(9), in which the ratio with respectto aluminum phosphate was more than 50.0 mass %, a non-uniformly whiteappearance was observed.

From the above results, the conditions under which both the peel forceand the appearance were favorable were the ones of the number C(3) tothe number C(8). Specifically, it was confirmed that favorable peelforce and appearance can be obtained when the ratio with respect toaluminum phosphate is 1.0 mass % to 50.0 mass %. Note that the ratiowith respect to aluminum phosphate before and after the baking is thesame. Namely, the ratio with respect to aluminum phosphate in the formedfilm is the same as that in the application liquid.

(Inorganic Powder)

A material of the inorganic powder is not limited to alumina. Forexample, it is conceivable that silica, magnesia, titania and zirconiaalso exhibit the same behavior as that of alumina. In order to confirmthis, the present inventors conducted experiments described below withrespect to these inorganics.

First, steel sheets were cold-rolled to a thickness of 0.35 mm and thenannealed at 920° C., thereby producing a plurality of steel sheets onwhich films were not formed.

Further, there were prepared application liquids formed by addingvarious ceramics powders having different BET specific surface areas andparticle size distributions (50% cumulative particle sizes and 90%cumulative particle sizes) to a mixed solution of 100 g of an aqueousaluminum biphosphate solution having a concentration of 50 mass % and 40g of an aqueous dispersion of acrylic organic resin having aconcentration of 30 mass %.

Further, the application liquids were coated on surfaces of the steelsheets and dried under a condition where an achieving temperature of thesteel sheets became 285° C. A coating amount of the application liquidwas set so that an amount of film after the drying (after the baking)became 2.3 g/m² per one side of the steel sheet.

Further, the same measurement and determination as those of theexperiments using the alumina powder were conducted. Specifically, themeasurement of peel force, the measurement of surface roughness Ra, andthe visual judgment of appearance were conducted. Results thereof areshown in Table 4.

TABLE 4 CONDITION OF POWDER RATIO OF BET ALUMINUM SPECIFIC CUMULATIVEWITH EVALUATION RESULT SURFACE PARTICLE RESPECT TO PEEL CONDITION TYPEOF AREA SIZE (μm) PHOSPHATE FORCE NUMBER POWDER (m²/g) 50% 90% (%) (g)DETERMINATION D 1 SILICA 280.4 1.3 4.1 0.5 385 X D 2 1.0 83 ◯ D 3 5.0 32⊚ D 4 10.0 25 ⊚ D 5 50.0 15 ⊚ D 6 75.0 10 ⊚ D 7 7.3 5.9 22.3 5.0 22 ⊚ D8 10.0 12 ⊚ D 9 50.0 10 ⊚ D 10 MAGNESIA 60.1 0.9 3.4 0.5 406 X D 11 1.079 ◯ D 12 5.0 39 ⊚ D 13 10.0 22 ⊚ D 14 50.0 13 ⊚ D 15 75.0 11 ⊚ D 16 2.37.4 25.4 5.0 29 ⊚ D 17 10.0 19 ⊚ D 18 50.0 11 ⊚ D 19 TITANIA 100.5 2.59.8 0.5 233 X D 20 1.0 59 ◯ D 21 5.0 44 ⊚ D 22 10.0 29 ⊚ D 23 50.0 18 ⊚D 24 75.0 10 ⊚ D 25 8.8 6.2 19.5 5.0 21 ⊚ D 26 10.0 15 ⊚ D 27 50.0 14 ⊚D 28 ZIRCONIA 48.0 3.3 10.1 0.5 611 X D 29 1.0 88 ◯ D 30 5.0 37 ⊚ D 3110.0 25 ⊚ D 32 50.0 16 ⊚ D 33 75.0 12 ⊚ D 34 9.8 8.4 18.1 5.0 35 ⊚ D 3510.0 18 ⊚ D 36 50.0 10 ⊚ EVALUATION RESULT CONDI- SURFACE TION ROUGHNESSCOMPREHENSIVE NUMBER Ra: μm DETERMINATION APPEARANCE DETERMINATIONDETERMINATION D 1 0.31 ⊚ UNIFORM ◯ X D 2 0.25 ⊚ UNIFORM ◯ ◯ D 3 0.39 ◯UNIFORM ◯ ◯ D 4 0.33 ⊚ UNIFORM ◯ ◯ D 5 0.41 ◯ UNIFORM ◯ ◯ D 6 0.58 ◯NON-UNIFORM X X D 7 0.99 X NON-UNIFORM X X D 8 1.23 X NON-UNIFORM X X D9 1.50 X NON-UNIFORM X X D 10 0.21 ⊚ UNIFORM ◯ ◯ D 11 0.26 ⊚ UNIFORM ◯ ◯D 12 0.32 ⊚ UNIFORM ◯ ◯ D 13 0.42 ◯ UNIFORM ◯ ◯ D 14 0.51 ◯ UNIFORM ◯ ◯D 15 0.68 ◯ NON-UNIFORM X X D 16 0.88 X NON-UNIFORM X X D 17 1.31 XNON-UNIFORM X X D 18 1.71 X NON-UNIFORM X X D 19 0.43 ◯ UNIFORM ◯ ◯ D 200.46 ◯ UNIFORM ◯ ◯ D 21 0.58 ◯ UNIFORM ◯ ◯ D 22 0.69 ◯ UNIFORM ◯ ◯ D 230.71 ◯ UNIFORM ◯ ◯ D 24 0.79 ◯ NON-UNIFORM X X D 25 0.95 X NON-UNIFORM XX D 26 1.22 X NON-UNIFORM X X D 27 1.88 X NON-UNIFORM X X D 28 0.29 ⊚UNIFORM ◯ X D 29 0.38 ◯ UNIFORM ◯ ◯ D 30 0.44 ◯ UNIFORM ◯ ◯ D 31 0.49 ◯UNIFORM ◯ ◯ D 32 0.61 ◯ UNIFORM ◯ ◯ D 33 0.70 ◯ NON-UNIFORM X X D 340.85 X NON-UNIFORM X X D 35 1.22 X NON-UNIFORM X X D 36 1.69 XNON-UNIFORM X X

As shown in Table 4, any of silica, magnesia, titania and zirconia wasconfirmed to show the same tendency as that of alumina. Specifically, anexcellent result was obtained when the BET specific surface area was 10m²/g or more, the 50% cumulative particle size and the 90% cumulativeparticle size were 5 μm or less and 15 μm or less, respectively,regarding the particle size distribution measured by the laserdiffraction particle size analyzer, and the ratio with respect toaluminum phosphate was 1.0 mass % to 50.0 mass %. Therefore, theseinorganic powders can also be used in the same manner as the aluminapowder. Further, these powders can also be combined to be used.

From the above description, it can be said that silica, magnesia,titania and zirconia can be used as an inorganic powder, similar toalumina. However, if cost, water dispersibility, handling workabilityand the like of the powder are taken into consideration, an aluminapowder is most suitable.

(Organic Resin)

The organic resin contained in the mixed solution used for forming thefilm is not particularly limited. For instance, a polyacrylic resin, apolystyrene resin, a polyethylene resin, a polyester resin, a polyolefinresin, a polyvinyl alcohol resin, a polypropylene resin, a polyamideresin, a polyurethane resin, a phenol resin, an epoxy resin and a vinylacetate resin can be used. Further, it is also possible that two kindsor more of these resins are combined to be used.

(Phosphate)

Phosphate is also not particularly limited. For example, magnesiumphosphate, calcium phosphate, zinc phosphate, potassium phosphate,sodium phosphate, nickel phosphate and the like, other than aluminumbiphosphate, can be used. Further, it is also possible that two kinds ormore of these phosphates are combined to be used. It is only required touse an aqueous solution of these phosphates at the time of forming thefilm.

(Baking Temperature of Film)

The present inventors also examined a range of baking temperature of thefilm.

First, steel sheets were cold-rolled to a thickness of 0.35 mm and thenannealed at 1020° C., thereby producing a plurality of steel sheets onwhich films were not formed.

Further, there was prepared an application liquid formed by adding 5 gof alumina powder having an average particle size of 100 nm and a BETspecific surface area of 120 m²/g to a mixed solution of 100 g of anaqueous aluminum biphosphate solution having a concentration of 50 mass% and 40 g of an aqueous dispersion of acrylic organic resin having aconcentration of 30 mass %.

Further, the application liquid was coated on surfaces of the steelsheets and dried under various achieving temperatures of the steelsheets. A coating amount of the application liquid was set so that anamount of film after the drying (after the baking) became 3.0 g/m² perone side of the steel sheet.

Thereafter, a peel force was measured in the same manner as that of theabove-described experiments. Results thereof are shown in Table 5.

TABLE 5 BAKING TEMPERATURE OF FILM PEEL FORCE NUMBER (° C.) (g)DETERMINATION E (1) 200 554 X E (2) 250 368 X E (3) 270 54 ◯ E (4) 28518 ⊚ E (5) 325 15 ⊚ E (6) 350 11 ⊚ E (7) 400 13 ⊚ E (8) 450 10 ⊚ E (9)500 12 ⊚

As shown in Table 5, under conditions of a number E(1) and a numberE(2), in which the baking temperature was lower than 270° C., the peelforces were large to be 554 g and 368 g, respectively. This indicatesthat the adhesion phenomenon occurred.

On the other hand, under conditions of a number E(3) to a number E(9),in which the baking temperature was 270° C. or higher, the peel forceswere small to be 54 g or less. This indicates that the adhesionphenomenon was prevented. In particular, under the conditions of thenumber E(4) to the number E(9), in which the baking temperature was 285°C. or higher, the peel forces were quite small to be 18 g or less. Thisindicates that the occurrence of adhesion phenomenon is particularlyeffectively prevented.

From the above results, it was confirmed that in order to suppress theadhesion phenomenon, the baking temperature of the film is preferably270° C. or higher, and more preferably 285° C. or higher.

Note that an upper limit of the baking temperature of the film is notparticularly limited.

(Baking Atmosphere of Film)

The present inventors also examined a baking atmosphere of the film.

The examined atmosphere includes a nitrogen atmosphere and an airatmosphere. Further, a dew point being an index that indicates aconcentration of water vapor in the atmosphere was also evaluated bysetting various conditions. As a result of this, a dependence of thestickiness and adhesion phenomenon on the atmosphere was notparticularly observed. Therefore, the baking atmosphere is notparticularly limited.

(Amount of Film)

The present inventors also examined an amount of film.

First, steel sheets were cold-rolled to a thickness of 0.5 mm and thenannealed at 850° C., thereby producing a plurality of steel sheets onwhich films were not formed.

Further, there was prepared an application liquid formed by adding 5 gof alumina powder having a 50% cumulative particle size of 0.55 μm, a90% cumulative particle size of 2.32 μm, and a BET specific surface areaof 190 m²/g to a mixed solution of 100 g of an aqueous aluminumbiphosphate solution having a concentration of 50 mass % and 40 g of anaqueous dispersion of acrylic organic resin having a concentration of 30mass %. Further, there was also prepared an application liquid to whichno alumina powder was added.

Further, surfaces of the steel sheets were coated with various amountsof the application liquid, and the drying was performed under acondition where an achieving temperature of the steel sheets became 375°C.

Thereafter, a peel force was measured in the same manner as that of theabove-described experiments. Results thereof are shown in Table 6.

TABLE 6 PRESENCE/ ABSENCE OF AMOUNT ADDITION OF FILM OF ALUMINA PEELFORCE NUMBER (g/m²) POWDER (g) DETERMINATION F (1) 1.0 PRESENCE 14 ⊚ F(2) 1.3 ″ 16 ⊚ F (3) 2.0 ″ 18 ⊚ F (4) 2.5 ″ 21 ⊚ F (5) 3.3 ″ 27 ⊚ F (6)4.5 ″ 32 ⊚ F (7) 5.4 ″ 40 ⊚ F (8) 6.5 ″ 48 ⊚ F (9) 1.0 ABSENCE 24 ⊚ F(10) 1.3 ″ 26 ⊚ F (11) 2.0 ″ 51 ◯ F (12) 2.5 ″ 101 X F (13) 3.3 ″ 206 XF (14) 4.5 ″ 385 X F (15) 5.4 ″ 603 X F (16) 6.5 ″ 920 X

As shown in Table 6, under each of conditions of a number F(1) to anumber F(8), in which the alumina powder was added, the peel force wassmall to be 14 g to 48 g. This indicates that the adhesion phenomenonwas prevented.

On the other hand, under conditions of a number F(9) and a number F(10),in which the alumina powder was not added, the peel forces were small tobe 24 g and 26 g, respectively. However, when compared to the numberF(1) and the number F(2) with the same amount of film, the peel forcesof the number F(9) and the number F(10) were large.

Further, under a condition of a number F(11), in which the aluminapowder was not added, the peel force was rather small to be 51 g.Accordingly, it cannot be clearly said that the adhesion phenomenonoccurred. However, the peel force under the condition of the numberF(11) was twice or more as large as that under the condition of thenumber F(3) with the same amount of film.

Further, under conditions of a number F(12) to a number F(16), in whichthe alumina powder was not added, the peel forces were large to be 100 gor more. Specifically, the peel forces of the number F(12) to the numberF(16) were remarkably larger than those of the number F(4) to the numberF(8) with the same amount of film. This indicates that the adhesionphenomenon occurred.

From the above results, it was confirmed that if the amount of film isat least within a range of 1.0 g/m² to 6.5 g/m², the peel force becomessmall in accordance with the addition of the alumina powder. Inparticular, when the amount of film is 2.0 g/m² or more, the decrease inthe peel force in accordance with the addition of the alumina powder issignificant, so that it was confirmed that the amount of film ispreferably 2.0 g/m² or more.

Note that an upper limit of the amount of film is not particularlylimited.

(Temperature Range)

The present inventors examined in which level of a temperature range inthe vicinity of room temperature the adhesion phenomenon is effectivelysuppressed.

First, steel sheets were cold-rolled to a thickness of 0.5 mm and thenannealed at 900° C., thereby producing a plurality of steel sheets onwhich films were not formed.

Further, there was prepared an application liquid formed by adding 5 gof alumina powder having a 50% cumulative particle size of 1.55 μm, a90% cumulative particle size of 3.57 μm, and a BET specific surface areaof 130 m²/g to a mixed solution of 100 g of an aqueous aluminumbiphosphate solution having a concentration of 50 mass % and 40 g of anaqueous dispersion of acrylic organic resin having a concentration of 30mass %.

Further, the application liquid was coated on surfaces of the steelsheets and dried under a condition where an achieving temperature of thesteel sheets became 375° C. A coating amount of the application liquidwas set so that an amount of film after the drying (after the baking)became 4.1 g/m² per one side of the steel sheet.

Thereafter, ten pieces of non-oriented electrical steel sheets were put,while being fixed, into a thermo-hygrostat in which the temperature waskept at −30° C. to +70° C. and the humidity was kept at 90%. This statesimulated a situation where the non-oriented electrical steel sheetsrolled in a coil shape are being transported.

Further, a peel force was measured in the same manner as that of theabove-described experiments. Results thereof are shown in Table 7.

TABLE 7 SET TEMPERATURE IN THERMO- HYGROSTAT THERMOSTATIC PEEL FORCENUMBER (° C.) (g) DETERMINATION G (1) −30 22 ⊚ G (2) −20 25 ⊚ G (3) −1021 ⊚ G (4) 0 20 ⊚ G (5) +10 23 ⊚ G (6) +30 27 ⊚ G (7) +50 24 ⊚ G (8) +6051 ◯ G (9) +70 101 X

As shown in Table 7, under each of conditions of a number G(1) to anumber G(8), in which the temperature was +60° C. or lower, the peelforce was small to be 21 g to 51 g. This indicates that the occurrenceof adhesion phenomenon was prevented.

On the other hand, under a condition of a number G(9), in which thetemperature was +70° C., the peel force was large to be 101 g. Thisindicates that the adhesion phenomenon was about to occur.

From the above results, it was confirmed that the adhesion phenomenon issuppressed when the temperature is at least within a range of −30° C. to+60° C. Specifically, the temperature after the stacking is preferably+60° C. or lower.

Note that a lower limit of the temperature after the stacking is notparticularly limited.

In recent years, manufacturing bases of motor cores have been increasingin Southeast Asian nations under an environment of high temperature andhigh humidity. Specifically, a demand of non-oriented electrical steelsheets on which inorganic-organic composite films are formed has beenincreasing in the Southeast Asian nations under the environment of hightemperature and high humidity. Meanwhile, the non-oriented electricalsteel sheets have been manufactured in another country, which is, forexample, Japan. Therefore, in many cases, the non-oriented electricalsteel sheets have been transported by ships. Accordingly, thesuppression of adhesion phenomenon leads to reduce workloads which havehad to be performed by the manufacture of motor cores.

Note that as long as the steel sheet, namely, the base material on whichthe inorganic-organic composite film is formed functions as anon-oriented electrical steel sheet, a composition thereof is notparticularly limited.

EXAMPLE Example 1

In an example 1, an effect of the present invention regarding an aluminapowder was verified. First, steel sheets were cold-rolled to a thicknessof 0.5 mm and then annealed at 880° C., thereby producing a plurality ofsteel sheets on which films were not formed.

Further, there was prepared an application liquid formed by adding 10 gof alumina powder having a 50% cumulative particle size of 0.35 μm, a90% cumulative particle size of 1.25 μm, and a BET specific surface areaof 220 m²/g to a mixed solution of 100 g of an aqueous aluminumbiphosphate solution having a concentration of 50 mass % and 40 g of anaqueous dispersion of acrylic organic resin having a concentration of 30mass %. Further, there was also prepared an application liquidcontaining no alumina powder.

Further, the application liquids were coated on surfaces of the steelsheets and dried under a condition where an achieving temperature of thesteel sheets became 315° C. A coating amount of the application liquidwas set so that an amount of film after the drying (after the baking)became 3.1 g/m² per one side of the steel sheet.

Thereafter, the measurement of peel force, the measurement of surfaceroughness Ra, and the visual judgment of appearance were conducted inthe same manner as that of the above-described experiments. Resultsthereof are shown in Table 8.

TABLE 8 CONDITION OF POWDER RATIO OF BET ALUMINUM SPECIFIC CUMULATIVEWITH EVALUATION RESULT SURFACE PARTICLE RESPECT TO PEEL TYPE OF AREASIZE (μm) PHOSPHATE FORCE CONDITION POWDER (m²/g) 50% 90% (%) (g)DETERMINATION EXAMPLE 1 ALUMINA 220 0.35 1.25 20.0 19 ⊚ COMPARATIVE NOADDITION OF ALUMINA POWDER 123 X EXAMPLE EVALUATION RESULT SURFACEROUGHNESS DETER- COMPREHENSIVE CONDITION Ra: μm DETERMINATION APPEARANCEMINATION DETERMINATION EXAMPLE 1 0.22 ⊚ UNIFORM ◯ ◯ COMPARATIVE 0.21 ⊚UNIFORM ◯ X EXAMPLE

As shown in Table 8, when the application liquid to which the aluminapowder was added was used, the peel force became small, compared to acase where the application liquid containing no alumina powder was used.Specifically, it was possible to suppress the adhesion phenomenon in theexample 1.

Example 2

In an example 2, an effect of the present invention regarding a silicapowder was verified. First, steel sheets were cold-rolled to a thicknessof 0.25 mm and then annealed at 1050° C., thereby producing a pluralityof steel sheets on which films were not formed.

Further, there was prepared an application liquid formed by adding 25 gof silica powder having a 50% cumulative particle size of 0.55 μm, a 90%cumulative particle size of 1.05 μm, and a BET specific surface area of380 m²/g to a mixed solution of 100 g of an aqueous aluminum biphosphatesolution having a concentration of 50 mass % and 40 g of an aqueousdispersion of acrylic organic resin having a concentration of 30 mass %.Further, there was also prepared an application liquid containing nosilica powder.

Further, the application liquids were coated on surfaces of the steelsheets and dried under a condition where an achieving temperature of thesteel sheets became 355° C. A coating amount of the application liquidwas set so that an amount of film after the drying (after the baking)became 3.9 g/m² per one side of the steel sheet.

Thereafter, the measurement of peel force, the measurement of surfaceroughness Ra, and the visual judgment of appearance were conducted inthe same manner as that of the above-described experiments. Resultsthereof are shown in Table 9.

TABLE 9 CONDITION OF POWDER RATIO OF BET ALUMINUM SPECIFIC CUMULATIVEWITH EVALUATION RESULT SURFACE PARTICLE RESPECT TO PEEL TYPE OF AREASIZE (μm) PHOSPHATE FORCE CONDITION POWDER (m²/g) 50% 90% (%) (g)DETERMINATION EXAMPLE 2 SILICA 380 0.55 1.05 50.0 15 ⊚ COMPARATIVE NOADDITION OF SILICA POWDER 223 X EXAMPLE EVALUATION RESULT SURFACEROUGHNESS DETER- COMPREHENSIVE CONDITION Ra: μm DETERMINATION APPEARANCEMINATION DETERMINATION EXAMPLE 2 0.19 ⊚ UNIFORM ◯ ◯ COMPARATIVE 0.18 ⊚UNIFORM ◯ X EXAMPLE

As shown in Table 9, when the application liquid to which the silicapowder was added was used, the peel force became small, compared to acase where the application liquid containing no silica powder was used.Specifically, it was possible to suppress the adhesion phenomenon in theexample 2.

Example 3

In an example 3, an effect of the present invention regarding a magnesiapowder was verified. First, steel sheets were cold-rolled to a thicknessof 0.55 mm and then annealed at 850° C., thereby producing a pluralityof steel sheets on which films were not formed.

Further, there was prepared an application liquid formed by adding 2.5 gof magnesia powder having a 50% cumulative particle size of 0.34 μm, a90% cumulative particle size of 2.12 μm, and a BET specific surface areaof 150 m²/g to a mixed solution of 100 g of an aqueous aluminumbiphosphate solution having a concentration of 50 mass % and 40 g of anaqueous dispersion of acrylic organic resin having a concentration of 30mass %. Further, there was also prepared an application liquidcontaining no magnesia powder.

Further, the application liquids were coated on surfaces of the steelsheets and dried under a condition where an achieving temperature of thesteel sheets became 285° C. A coating amount of the application liquidwas set so that an amount of film after the drying (after the baking)became 2.0 g/m² per one side of the steel sheet.

Thereafter, the measurement of peel force, the measurement of surfaceroughness Ra, and the visual judgment of appearance were conducted inthe same manner as that of the above-described experiments. Resultsthereof are shown in Table 10.

TABLE 10 CONDITION OF POWDER RATIO OF BET ALUMINUM SPECIFIC CUMULATIVEWITH EVALUATION RESULT SURFACE PARTICLE RESPECT TO PEEL TYPE OF AREASIZE (μm) PHOSPHATE FORCE CONDITION POWDER (m²/g) 50% 90% (%) (g)DETERMINATION EXAMPLE 3 MAGNESIA 150 0.34 2.12 5.0 19 ⊚ COMPARATIVE NOADDITION OF MAGNESIA POWDER 123 X EXAMPLE EVALUATION RESULT SURFACEROUGHNESS DETER- COMPREHENSIVE CONDITION Ra: μm DETERMINATION APPEARANCEMINATION DETERMINATION EXAMPLE 3 0.25 ⊚ UNIFORM ◯ ◯ COMPARATIVE 0.24 ⊚UNIFORM ◯ X EXAMPLE

As shown in Table 10, when the application liquid to which the magnesiapowder was added was used, the peel force became small, compared to acase where the application liquid containing no magnesia powder wasused. Specifically, it was possible to suppress the adhesion phenomenonin the example 3.

Example 4

In an example 4, an effect of the present invention regarding a titaniapowder was verified. First, steel sheets were cold-rolled to a thicknessof 0.45 mm and then annealed at 930° C., thereby producing a pluralityof steel sheets on which films were not formed.

Further, there was prepared an application liquid formed by adding 3.0 gof titania powder having a 50% cumulative particle size of 2.56 μm, a90% cumulative particle size of 8.92 μm, and a BET specific surface areaof 220 m²/g to a mixed solution of 100 g of an aqueous aluminumbiphosphate solution having a concentration of 50 mass % and 40 g of anaqueous dispersion of acrylic organic resin having a concentration of 30mass %. Further, there was also prepared an application liquidcontaining no titania powder.

Further, the application liquids were coated on surfaces of the steelsheets and dried under a condition where an achieving temperature of thesteel sheets became 315° C. A coating amount of the application liquidwas set so that an amount of film after the drying (after the baking)became 2.5 g/m² per one side of the steel sheet.

Thereafter, the measurement of peel force, the measurement of surfaceroughness Ra, and the visual judgment of appearance were conducted inthe same manner as that of the above-described experiments. Resultsthereof are shown in Table 11.

TABLE 11 CONDITION OF POWDER RATIO OF BET ALUMINUM SPECIFIC CUMULATIVEWITH EVALUATION RESULT SURFACE PARTICLE RESPECT TO PEEL TYPE OF AREASIZE (μm) PHOSPHATE FORCE CONDITION POWDER (m²/g) 50% 90% (%) (g)DETERMINATION EXAMPLE 4 TITANIA 220 2.56 8.92 6.0 11 ⊚ COMPARATIVE NOADDITION OF TITANIA POWDER 108 X EXAMPLE EVALUATION RESULT SURFACEROUGHNESS DETER- COMPREHENSIVE CONDITION Ra: μm DETERMINATION APPEARANCEMINATION DETERMINATION EXAMPLE 4 0.45 ◯ UNIFORM ◯ ◯ COMPARATIVE 0.43 ◯UNIFORM ◯ X EXAMPLE

As shown in Table 11, when the application liquid to which the titaniapowder was added was used, the peel force became small, compared to acase where the application liquid containing no titania powder was used.Specifically, it was possible to suppress the adhesion phenomenon in theexample 4.

Example 5

In an example 5, an effect of the present invention regarding a zirconiapowder was verified. First, steel sheets were cold-rolled to a thicknessof 0.35 mm and then annealed at 990° C., thereby producing a pluralityof steel sheets on which films were not formed.

Further, there was prepared an application liquid formed by adding 1.0 gof zirconia powder having a 50% cumulative particle size of 4.33 μm, a90% cumulative particle size of 10.12 μm, and a BET specific surfacearea of 90 m²/g to a mixed solution of 100 g of an aqueous aluminumbiphosphate solution having a concentration of 50 mass % and 40 g of anaqueous dispersion of acrylic organic resin having a concentration of 30mass %. Further, there was also prepared an application liquidcontaining no zirconia powder.

After that, the application liquids were coated on surfaces of the steelsheets and dried under a condition where an achieving temperature of thesteel sheets became 315° C. A coating amount of the application liquidwas set so that an amount of film after the drying (after the baking)became 2.5 g/m² per one side of the steel sheet.

Thereafter, the measurement of peel force, the measurement of surfaceroughness Ra, and the visual judgment of appearance were conducted inthe same manner as that of the above-described experiments. Resultsthereof are shown in Table 12.

TABLE 12 CONDITION OF POWDER RATIO OF BET ALUMINUM SPECIFIC CUMULATIVEWITH EVALUATION RESULT SURFACE PARTICLE RESPECT TO PEEL TYPE OF AREASIZE (μm) PHOSPHATE FORCE CONDITION POWDER (m²/g) 50% 90% (%) (g)DETERMINATION EXAMPLE 5 ZIRCONIA 90 4.33 10.12 2.0 13 ⊚ COMPARATIVE NOADDITION OF ZIRCONIA POWDER 145 X EXAMPLE EVALUATION RESULT SURFACEROUGHNESS DETER- COMPREHENSIVE CONDITION Ra: μm DETERMINATION APPEARANCEMINATION DETERMINATION EXAMPLE 5 0.36 ◯ UNIFORM ◯ ◯ COMPARATIVE 0.33 ⊚UNIFORM ◯ X EXAMPLE

As shown in Table 12, when the application liquid to which the zirconiapowder was added was used, the peel force became small, compared to acase where the application liquid containing no zirconia powder wasused. Specifically, it was possible to suppress the adhesion phenomenonin the example 5.

Examples 6 to 11, Comparative Examples 12 to 17

In examples 6 to 11 and comparative examples 12 to 17, various organicresins were used, and further, various ceramics powders were used asinorganic powders. First, steel sheets were cold-rolled to a thicknessof 0.5 mm and then annealed at 950° C., thereby producing a plurality ofsteel sheets on which films were not formed.

Further, there were prepared application liquids formed by adding eachof the ceramics powders to a mixed solution of 100 g of an aqueousaluminum biphosphate solution having a concentration of 50 mass % and 40g of an aqueous dispersion of acrylic organic resin having aconcentration of 30 mass %. The types of the organic resins, materialsand amounts of the ceramics powders are shown in Table 13. Note that“ratio with respect to solid content of phosphate” indicates a ratio ofa mass (g) of alumina powder, silica powder, titania powder or zirconiapowder with respect to a solid content (g) of aluminum biphosphatecontained in an aqueous aluminum biphosphate solution having aconcentration of 50 mass %.

Further, the application liquids were coated on surfaces of the steelsheets and dried under a condition where an achieving temperature of thesteel sheets became 320° C. A coating amount of the application liquidwas set so that an amount of film after the drying (after the baking)became 3.5 g/m² per one side of the steel sheet.

Thereafter, the measurement of peel force, the measurement of surfaceroughness Ra, and the visual judgment of appearance were conducted inthe same manner as that of the above-described experiments. Resultsthereof are shown in Table 13.

TABLE 13 INORGANIC POWDER MEASUREMENT USING LASER RATIO SPECIFICSCATTERING/DIFFRACTION WITH SURFACE PARTICLE SIZE RESPECT AREADISTRIBUTION METER TO SOLID MEASURED 50% 90% CONTENT BY BET CUMULATIVECUMULATIVE OF METHOD PARTICLE PARTICLE PHOSPHATE ORGANIC RESIN CONDITIONTYPE (m²/g) SIZE (μm) SIZE (μm) (%) TYPE EXAMPLE 6 ALUMINA 10.0 3.8 12.112 POLYACRYL EXAMPLE 7 SILICA 22.5 5.0 13.8 25 POLYSTYRENE EXAMPLE 8TITANIA 56.1 4.1 15.0 35 POLYETHYLENE EXAMPLE 9 ZIRCONIA 128.5 2.2 7.3 1VINYL ACETATE EXAMPLE 10 ALUMINA 326.8 3.8 5.6 50 POLYPROPYLENE EXAMPLE11 ALUMINA 221.5 1.5 7.6 10 POLYACRYL- STYRENE COMPARATIVE ALUMINA 3.14.1 10.5 10 POLYACRYL EXAMPLE 12 COMPARATIVE SILICA 20.5 8.7 14.2 20POLYSTYRENE EXAMPLE 13 COMPARATIVE TITANIA 45.7 4.4 25.9 30 POLYETHYLENEEXAMPLE 14 COMPARATIVE ZIRCONIA 120.3 3.2 12.6 0.5 VINYL ACETATE EXAMPLE15 COMPARATIVE ALUMINA 210.8 4.9 13.7 75 POLYPROPYLENE EXAMPLE 16COMPARATIVE ALUMINA 2.4 6.1 16.3 60 POLYACRYL- EXAMPLE 17 STYRENE RESULTOF PROPERTY EVALUATION ADHESION RESISTANCE SURFACE PEEL ROUGHNESS FORCERa EVALUA- APPEARANCE COMPREHENSIVE CONDITION (g) EVALUATION (μm) TIONVISUAL EVALUATION DETERMINATION EXAMPLE 6 32 ⊚ 0.45 ◯ UNIFORM ◯ ◯EXAMPLE 7 21 ⊚ 0.61 ◯ UNIFORM ◯ ◯ EXAMPLE 8 36 ⊚ 0.72 ◯ UNIFORM ◯ ◯EXAMPLE 9 45 ⊚ 0.21 ⊚ UNIFORM ◯ ◯ EXAMPLE 10 15 ⊚ 0.42 ◯ UNIFORM ◯ ◯EXAMPLE 11 19 ⊚ 0.29 ⊚ UNIFORM ◯ ◯ COMPARATIVE 101 X 0.51 ◯ UNIFORM ◯ XEXAMPLE 12 COMPARATIVE 24 ⊚ 0.94 X UNIFORM ◯ X EXAMPLE 13 COMPARATIVE 36⊚ 1.01 X UNIFORM ◯ X EXAMPLE 14 COMPARATIVE 136 X 0.76 ◯ UNIFORM ◯ XEXAMPLE 15 COMPARATIVE 22 ⊚ 0.68 ◯ NON- X X EXAMPLE 16 UNIFORMCOMPARATIVE 101 X 1.26 X NON- X X EXAMPLE 17 UNIFORM

As shown in Table 13, in the comparative example 12 to the comparativeexample 17, in which at least one of the BET specific surface area, theparticle size distribution or the ratio with respect to solid content ofphosphate is out of the range of the present invention, the evaluationof at least one of the peel force, the surface roughness or theappearance was lowered. Therefore, a comprehensive determination of thecomparative examples was made as ×. Meanwhile, the examples 6 to 11, inwhich the BET specific surface area, the particle size distribution orthe ratio with respect to solid content of phosphate were within therange of the present invention achieved high evaluation in every item,so that a comprehensive determination thereof was made as ◯.

INDUSTRIAL APPLICABILITY

The present invention can be utilized in, for example, an electricalsteel sheet manufacturing industry and an industry using electricalsteel sheets.

1. A manufacturing method of a non-oriented electrical steel sheet,comprising: coating an application liquid which contains an inorganiccomponent and an organic resin on a surface of a steel sheet; andforming an inorganic-organic composite film by baking the applicationliquid on the surface of the steel sheet, wherein the application liquidcontains phosphate as the inorganic component, and wherein theapplication liquid further contains an inorganic powder having a BETspecific surface area of 10 m²/g or more and exhibiting a particle sizedistribution with a 50% cumulative particle size of 5 μm or less andwith a 90% cumulative particle size of 15 μm or less when measured by alaser diffraction particle size analyzer, the powder being contained ata ratio of no less than 1 mass %, nor more than 50 mass % with respectto a solid content of the phosphate.
 2. The manufacturing method of anon-oriented electrical steel sheet according to claim 1, wherein theapplication liquid does not contain a chromate-based compound.
 3. Themanufacturing method of a non-oriented electrical steel sheet accordingto claim 1, wherein the application liquid contains, as the inorganicpowder, at least one kind selected from a group consisting of aluminapowder, silica powder, magnesia powder, titania powder and zirconiapowder.
 4. The manufacturing method of a non-oriented electrical steelsheet according to claim 2, wherein the application liquid contains, asthe inorganic powder, at least one kind selected from a group consistingof alumina powder, silica powder, magnesia powder, titania powder andzirconia powder.
 5. The manufacturing method of a non-orientedelectrical steel sheet according to claim 1, wherein the applicationliquid is formed of a mixed solution of an aqueous aluminum biphosphatesolution and an aqueous dispersion of organic resin, and the inorganicpowder.
 6. The manufacturing method of a non-oriented electrical steelsheet according to claim 2, wherein the application liquid is formed ofa mixed solution of an aqueous aluminum biphosphate solution and anaqueous dispersion of organic resin, and the inorganic powder.
 7. Themanufacturing method of a non-oriented electrical steel sheet accordingto claim 3, wherein the application liquid is formed of a mixed solutionof an aqueous aluminum biphosphate solution and an aqueous dispersion oforganic resin, and the inorganic powder.
 8. The manufacturing method ofa non-oriented electrical steel sheet according to claim 4, wherein theapplication liquid is formed of a mixed solution of an aqueous aluminumbiphosphate solution and an aqueous dispersion of organic resin, and theinorganic powder.
 9. The manufacturing method of a non-orientedelectrical steel sheet according to claim 1, wherein a temperature atthe baking the application liquid on the surface of the steel sheet isset to 270° C. or higher.
 10. The manufacturing method of a non-orientedelectrical steel sheet according to claim 2, wherein a temperature atthe baking the application liquid on the surface of the steel sheet isset to 270° C. or higher.
 11. The manufacturing method of a non-orientedelectrical steel sheet according to claim 3, wherein a temperature atthe baking the application liquid on the surface of the steel sheet isset to 270° C. or higher.
 12. The manufacturing method of a non-orientedelectrical steel sheet according to claim 4, wherein a temperature atthe baking the application liquid on the surface of the steel sheet isset to 270° C. or higher.
 13. The manufacturing method of a non-orientedelectrical steel sheet according to claim 5, wherein a temperature atthe baking the application liquid on the surface of the steel sheet isset to 270° C. or higher.
 14. The manufacturing method of a non-orientedelectrical steel sheet according to claim 6, wherein a temperature atthe baking the application liquid on the surface of the steel sheet isset to 270° C. or higher.
 15. The manufacturing method of a non-orientedelectrical steel sheet according to claim 7, wherein a temperature atthe baking the application liquid on the surface of the steel sheet isset to 270° C. or higher.
 16. The manufacturing method of a non-orientedelectrical steel sheet according to claim 8, wherein a temperature atthe baking the application liquid on the surface of the steel sheet isset to 270° C. or higher.
 17. A non-oriented electrical steel sheet,comprising an inorganic-organic composite film formed on a surface,wherein said inorganic-organic composite film contains: phosphate; andan inorganic powder having a BET specific surface area of 10 m²/g ormore and exhibiting a particle size distribution with a 50% cumulativeparticle size of 5 μm or less and with a 90% cumulative particle size of15 μm or less when measured by a laser diffraction particle sizeanalyzer, and wherein a content of the inorganic powder is no less than1 mass %, nor more than 50 mass % with respect to a solid content of thephosphate.
 18. The non-oriented electrical steel sheet according toclaim 17, wherein said inorganic-organic composite film does not containa chromate-based compound.
 19. The non-oriented electrical steel sheetaccording to claim 17, wherein said inorganic-organic composite filmcontains, as the inorganic powder, at least one kind selected from agroup consisting of alumina powder, silica powder, magnesia powder,titania powder and zirconia powder.
 20. The non-oriented electricalsteel sheet according to claim 18, wherein said inorganic-organiccomposite film contains, as the inorganic powder, at least one kindselected from a group consisting of alumina powder, silica powder,magnesia powder, titania powder and zirconia powder.
 21. An applicationliquid for a non-oriented electrical steel sheet, containing: phosphateas an inorganic component; and an inorganic powder having a BET specificsurface area of 10 m²/g or more and exhibiting a particle sizedistribution with a 50% cumulative particle size of 5 μm or less andwith a 90% cumulative particle size of 15 μm or less when measured by alaser diffraction particle size analyzer, the powder being contained ata ratio of no less than 1 mass %, nor more than 50 mass % with respectto a solid content of said phosphate.
 22. The application liquid for anon-oriented electrical steel sheet according to claim 21, wherein achromate-based compound is not contained.
 23. The application liquid fora non-oriented electrical steel sheet according to claim 21, wherein atleast one kind selected from a group consisting of alumina powder,silica powder, magnesia powder, titania powder and zirconia powder iscontained as said inorganic powder.
 24. The application liquid for anon-oriented electrical steel sheet according to claim 22, wherein atleast one kind selected from a group consisting of alumina powder,silica powder, magnesia powder, titania powder and zirconia powder iscontained as said inorganic powder.